Animal carcasses, such as for example hog carcasses and the like, soon after slaughter, are hung to allow bodily fluids to drain, are also washed for cleanliness, and are surface scalded to assist removal of body hair. In the case of hogs in particular, the washing step includes the washing of the carcass with hot water, followed by a process known as scalding. The purpose of surface scalding is generally to soften the hair on the carcass so that it may be more readily removed.
In the past, these operations have been carried out usually by first of all hanging the carcass vertically by one leg from a hanging rail for drainage. The carcasses were then taken off the rail and were washed and scalded by simply dipping them in a tank of water. These somewhat rudimentary processing steps are time consuming, relatively inefficient, and do not lend themselves to increased cleanliness. In addition, they also produce some harmful side effects on the carcass, in which the quality of some of the meat may be reduced, at least bacteriologically.
Hanging the carcass by one leg for any length of time is found to result in distortion of the muscle, fat or joint in that leg. It is also found that due to the tension on the muscle in that leg, the draining of body fluids from that muscle is sometimes incomplete. It is felt desirable that the leg muscles of the carcass should be relaxed at some time during this draining stage.
The washing and scalding step, when it is carried out in a tank of water, is not completely satisfactory. In addition, the tank must be emptied and flushed out and refilled regularly, which is expensive, energy inefficient, and labour consuming.
The use of large open tanks of hot water results in substantial energy losses due to heat loss and evaporation, and uneven scalding of the carcasses, and may cause loss of meat product.
It is, therefore, desirable as far as possible that carcasses should be washed in such a manner that all the dirt from each carcass be flushed away, and the surface of the carcass should then be scalded, free of dirt.
In addition, it is desirable to provide for an improved method of hanging the carcasses for drainage, which results in complete drainage, with minimum retention of fluids in the muscles.
It is also clearly desirable that the various steps of hanging, washing, etc., shall be carried out without the requirement for unnecessary handling of each carcass.
In the particular case of the scalding of carcasses, it is desirable for best results that the water shall be at a fairly high temperature in the range of between 55 to 65 degrees.
It is, however, generally considered that if the carcass is subjected to this temperature immediately, or is subjected to this temperature for too great a length of time, that certain undesirable effects can result, causing loss of quality in the carcass and lower grades of certain cuts. On the other hand, if the surfacing scalding is not carried out for a sufficiently long period of time, then the hair is not fully treated, and hair removal will not be completely satisfactory.
It is therefore desirable to find some means whereby these two somewhat conflicting objectives can be satisfied namely, achieving adequate scalding of the carcass so as to ensure satisfactory hair removal, without loss of meat quality.